1. Field of the Invention
The present invention relates to a linear guide apparatus provided with infinite circulating paths of rolling balls interposed between a guide rail and a slider movable on the guide rail, and in particular, to a linear guide apparatus having a wire ball retainer for holding the balls.
2. Description of the Relevant Art
A linear guide apparatus of this type is disclosed, for example, in U.S. Pat. No. 4,472,003. In this linear guide apparatus, as shown in FIGS. 1 and 2, a slider 4 is formed with an axial recess 1, having a pair of axial ball rolling grooves 2 formed in the inner vertical surfaces of the recess 1 and axial through holes 3 bored laterally from and parallel to the ball rolling grooves 2. An elongate guide rail 10 has axial ball rolling grooves 9 respectively corresponding to the ball rolling grooves 2 of the slider 4. End caps 6 are respectively secured to opposite ends of the slider 4, and each of the end caps 6 has a semicircular ball path 5 for connecting the opposing ball rolling grooves 2 and 9 to the through hole 3 of the slider 4. Additionally, each end cap 6 has a return guide G of a semicircular shape fixed at the inside of the ball path 5. A multiplicity of balls 7 are filled rollably between the opposing ball rolling grooves 2 and 9, in the through holes 3 and ball paths 5. To hold the balls 7, a wire retainer 8 is provided.
When the slider 4 moves relative to the guide rail 1 in an axial direction, the balls 7 roll and circulate through the through hole 3, semicircular ball paths 5, and ball rolling grooves 2 and 9, and hence the slider 4 can travel smoothly in the axial direction due to the rolling of the balls 7.
The wire retainer 8 is provided for the purpose of preventing the balls 7 from falling off the ball rolling grooves 2 of the slider 4 when the slider 4 is removed from the guide rail 10. When the slider 4 is being fitted to the guide rail 10, the wire retainer 8 is accommodated in a wire escape channel 9a, formed in the bottom of the ball rolling groove 9, thereby preventing interference with the ball rolling groove 9 and ensuring the smooth rolling of the balls 7.
However, the wire retainer 8 of the prior art linear guide apparatus has semicircular bent portions 11 at opposite ends thereof, and the bent portions 11 are merely fitted into wire escape channels 5a formed in the semicircular ball paths 5 of the end caps 6 in order to hold the wire retainer 8. In such a structure, the fitting of the bent portions 11 of the wire retainer 8 to the wire escape channels 5a formed in the end caps 6 is not so rigid. As a result, problems have been experienced in that the wire retainer 8 tends to be loosened thus causing interference with the wire escape channel 9a, thereby disturbing the smooth rolling of the balls 7.
Furthermore, when the slider 4 is removed from the guide rail 10, the balls 7 fall off due to a shock imparted to the slider 4.